The present invention relates to a seat slide device to be used for adjusting seat position in vehicles.
In a conventional seat slide device (as disclosed in the Japanese Utility Model Laid-Open Publication No. Hei 5-37553), as shown in FIG. 11, the position of a seat sliding along a lower rail L arranged on the floor of a vehicle is adjusted by moving an upper rail U supporting the seat with respect to the lower rail L, by an operation of an electric motor through a drive unit K. A bracket B housing the drive unit K therein and retaining one end of a screw member S arranged in the lower rail L is fixed on the top face T of one end of the upper rail U by means of a plurality of bolts BT.
In this seat slide device of the prior art, a serious impact load is applied at a time of collision of the vehicle to the seat so that it has to be borne by a reduction gear mechanism of the drive unit K and by the bracket B and the screw member S.
As shown in FIG. 11, a distance h is made between a load F to act on the top face T of the upper rail U and a load F' to act on the screw member S, so that a cantilever support structure is made to apply the bending moment of F' .cndot.h to the bracket B. As a result, the bracket B may be deformed or broken, as shown in FIG. 12, when the serious load (e.g., a reaction at the time when the seat is moved in the longitudinal direction by the impact) acts from the seat at collision of the vehicle. In order to avoid this deformation or breakage of the bracket B, it is necessary to increase the thickness of the bracket B or to change the shape for enhancing the strength. This raises a problem to invite a large size or a high cost of the seat slide device.